Focal segmental glomerulosclerosis (FSGS) manifests with heavy proteinuria in association with focal, but progressive, glomerular sclerosis in the kidney [1-3]. The frequency of end-stage renal disease in patients with FSGS was found to be as high as 78% in long-term follow-up studies [4,5]. Although corticosteroids and other immunomodulatory agents are commonly used to treat these patients [6,7], they result in an unsatisfactory outcome in terms of progression of renal inflammation and fibrosis [8,9] and have various side-effects [10,11]. In addition, the administration of such agents is mostly based on empirical decisions, rather than on targeting specific pathogenic pathways [12]. The establishment of a pathogenesis-based therapeutic strategy is therefore clinically significant.
Citral, that is, 3,7-dimethyl-2,6-octadienal, is an unsaturated chain aldehyde monoterpene containing two double bonds. There are two isomers of citral, with the following structures:

Normally, citral is a mixture of the above two isomers and can be obtained by extraction from citrus plants. It is an oil-like, volatile pale yellow liquid with a lemon scent. Due to its strong lemon scent and taste, citral has been extensively utilized in the cosmetic industry, for example, in perfumes; it has also been used as a safe food additive, for example, in spices. Current studies also showed that citral has anti-bacterial activity, anti-fungal activity and resistance to the genotoxicity induced by the anti-cancer drug bleomycin (see Karabörklü S et al., Journal of economic entomology. 104(4):1212-9, 2011; Molkary Andrea Lôpez et al., Genetics and Molecular Biology. 34(3): 479-488, 2011; Singh S A et al., Natural Product Communications. 6(9):1221-4, 2011; or Zore G B et al., Phytomedicine. 18(13):1181-90, 2011). However, no prior art references has disclosed the use of citral in the treatment of focal segmental glomerulosclerosis.